The present invention relates to a nut having a nut segment which, after a bolt is inserted into the nut segment, is screwed on to the threaded portion of the bolt.
A conventional nut of this kind is comprised of: a nut body having an outer wall formed in the shape of a polygon and an inner wall having an inclined hole of which diameter decreases gradually; a stopper plate having a bolt insertion hole formed at a larger diameter end of the nut body; at least three or more guideposts formed coaxially on the inner wall surface of the nut body; at least three or more nut segments being movably disposed between the guideposts so as to permit sliding movement in an axial direction, each of the nut segments having an inner surface having a screw thread for engaging a thread of the bolt; an attachment piece, which is formed in the shape of a flange, fixed at a smaller diameter end of the nut body, the attachment piece prevents the at least three or more nut segments from falling off, projects outwardly of the outer circumferential surface of the nut body; and an urging spring received in the nut body to bias the at least three or more nut segments toward the smaller diameter end of the nut body.
In the above-mentioned structure, the nut, when rotated in the tightening direction after the bolt is inserted into the nut segments, makes the three nut segments screwed on to the thread portion of the bolt. However, a drawback is that there may or may not always be a clearance about one pitch width of a thread.
Patent document 1: Japanese published unexamined application H11-72110